Trailer assist system with enhanced beam length estimation

ABSTRACT

A vehicular trailering assist system for a vehicle includes a camera disposed at a rear portion of a vehicle and having a field of view exterior and at least rearward of the vehicle, the field of view encompassing at least a portion of a trailer hitched to the vehicle. A control includes a processor for processing image data captured by the camera and sensor data captured by a steering wheel angle sensor and a wheel RPM sensor. The control determines a trailer angle of the trailer relative to the vehicle, a steering wheel angle, and a wheel RPM of a wheel of the vehicle. The control estimates a trailer beam length based on at least the determined trailer angle, the determined steering wheel angle, and the determined wheel RPM.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. provisional applications,Ser. No. 62/952,748, filed Dec. 23, 2019, Ser. No. 62/938,411, filedNov. 21, 2019, and Ser. No. 62/868,051, filed Jun. 28, 2019, which arehereby incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to a vehicle vision system for avehicle and, more particularly, to a vehicle vision system that utilizesone or more cameras at a vehicle.

BACKGROUND OF THE INVENTION

Use of imaging sensors in vehicle imaging systems is common and known.Examples of such known systems are described in U.S. Pat. Nos.5,949,331; 5,670,935 and/or 5,550,677, which are hereby incorporatedherein by reference in their entireties. Trailer assist systems areknown that may determine an angle of a trailer hitched at a vehicle.Examples of such known systems are described in U.S. Pat. Nos. 9,085,261and/or 6,690,268, which are hereby incorporated herein by reference intheir entireties.

SUMMARY OF THE INVENTION

The present invention provides a driver assistance system or visionsystem or imaging system for a vehicle that utilizes a camera disposedat a rear portion of a vehicle and having a field of view exterior ofthe vehicle, the field of view encompassing at least a portion of atrailer hitched to the vehicle. The system also includes a steeringwheel angle sensor operable to determine a steering wheel angle of thevehicle and a wheel revolutions per minute (RPM) sensor operable todetermine an RPM of a wheel of the vehicle. The system also includes acontrol comprising an image processor operable to process image datacaptured by the camera and sensor data captured by the sensors, with theimage data captured by the camera representative of the trailer hitchedto the vehicle. The control, responsive to processing of image datacaptured by the camera, determines a trailer angle of the trailerrelative to the vehicle and may determine or be provided with a hitchlocation relative to a rear axle of the vehicle. The control, responsiveto processing of sensor data from the steering wheel angle sensor andthe RPM sensor determines a steering wheel angle of the vehicle and awheel RPM of the vehicle. The control estimates a trailer beam lengthusing the determined trailer angle, the determined steering wheel angle,and the determined wheel RPM. The determined or provided hitch locationrelative to the rear axle of the vehicle may also be used in the trailerbeam length estimation.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a vehicle with a trailer assist system that isoperable to steer a trailer along a trailer direction in accordance withthe present invention;

FIG. 2 is a block diagram of the trailer assist system of FIG. 1;

FIGS. 3A and 3B are detailed block diagrams of the block diagram of FIG.2; and

FIG. 4 is a table of exemplary calculations of max front wheel anglesand corresponding max trailer beam length.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A vehicle and trailer maneuvering system or maneuver assist systemand/or driving assist system operates to capture images exterior of thevehicle and of a trailer being towed by the vehicle and may process thecaptured image data to determine a path of travel for the vehicle andtrailer and to detect objects at or near the vehicle and in thepredicted path of the vehicle, such as to assist a driver of the vehiclein maneuvering the vehicle and trailer in a rearward direction. Thevision system includes an image processor or image processing systemthat is operable to receive image data from one or more cameras and thatmay provide an output to a display device for displaying imagesrepresentative of the captured image data. Optionally, the vision systemmay provide a display, such as a rearview display or a top down orbird's eye or surround view display or the like.

Referring now to the drawings and the illustrative embodiments depictedtherein, a vehicle 10 includes a trailer assist system 12 (such as partof a rear backup assist system) that is operable to assist in backing upor reversing the vehicle with a hitched trailer that is hitched at therear of the vehicle via a trailer hitch 14, and the system may maneuverthe vehicle 10 and trailer 16 toward a desired or selected location. Thetrailer assist system 12 includes at least one exterior viewingvehicle-based imaging sensor or camera, such as a rearward viewingimaging sensor or camera 18, which may comprise a rear backup camera ofthe vehicle (and the system may optionally include multiple exteriorviewing imaging sensors or cameras, such as a sideward/rearward viewingcamera at respective sides of the vehicle), which captures image datarepresentative of the scene exterior and at least rearward of thevehicle 10, with the field of view of the camera encompassing thetrailer hitch 14 and/or trailer 16, and with the camera 18 having a lensfor focusing images at or onto an imaging array or imaging plane orimager of the camera (FIG. 1). Optionally, a forward viewing camera maybe disposed at the windshield of the vehicle 10 and view through thewindshield and forward of the vehicle 10, such as for a machine visionsystem (such as for traffic sign recognition, headlamp control,pedestrian detection, collision avoidance, lane marker detection and/orthe like). The trailer assist system 12 includes a control 11 orelectronic control unit (ECU) having electronic circuitry and associatedsoftware, with the electronic circuitry including a data processor orimage processor that is operable to process image data captured by thecamera or cameras and that may detect objects or the like and/or providedisplayed images at a display device for viewing by the driver of thevehicle (the control and/or display device may be part of orincorporated in or at an interior rearview mirror assembly of thevehicle, or the control and/or the display device may be disposedelsewhere at or in the vehicle). The data transfer or signalcommunication from the camera to the ECU may comprise any suitable dataor communication link, such as a vehicle network bus or the like of theequipped vehicle. The system 12 may also include one or more sensors 19.For example, a steering wheel angle sensor and/or a revolution perminute (RPM) wheel sensor.

Trailer beam length is an important if not essential parameter for manyautomated trailering applications (e.g., reversing, jackknifeprevention, parking, etc.) because automated trailering requiresaccurate position and heading predictions for the vehicle-trailersystem. The accuracy of these kinematic predictions depends on themeasurement accuracy of parameters such as beam length. Trailer beamlength for single-axle trailers is defined as the length from the hitchpoint to the rear axle. For multi-axle trailers, the effective kinematictrailer beam length is defined as the length from the hitch point to anintermediate point between the multiple axles. Ideally, beam length ismeasured or estimated or determined using an automatic or online method,as otherwise the user or driver must manually measure every time adifferent trailer is hitched. Manual measuring of beam length can bedifficult, especially for long and/or multi-axle trailers. Additionally,the accuracy of such measurements is highly dependent upon the user andthe tool used.

Implementations of the present invention estimate trailer beam lengthonline using vehicle and trailer kinematics with input from vehiclesensors (e.g., a visual hitch point detection system and a trailer angledetection system). Implementations provided estimate the trailer beamlength for any trailer currently hitched to the vehicle with minimaluser setup requirements and eliminates the need for the driver tomanually measure.

Referring now to FIG. 2, the trailer assist system 12 includes a trailerangle and hitch detection system 22 (e.g., a hitch location and trailerangle). Other vehicle sensors 19 may also be included (e.g., to measurevehicle speed, wheel angle, etc.). The system, as discussed in moredetail below, directs a driver to undergo calibration driving maneuvers.During these maneuvers, the system processes data from these sensors andcameras and passes the data to an online trailer beam length estimator25 that estimates a trailer beam length 27 at a trailer beam lengthcalculator 26. The estimator 25 may then conduct a convergence check 28.If there is not a convergence (i.e., convergence is false), thecalculator 26 again estimates the trailer beam length 27. If there isconvergence (i.e., convergence is true), the estimator 25 stores thebeam length estimation 27 in non-volatile memory and prompts the userthat calibration is complete.

Referring now to FIG. 3A, in some examples, the trailer angle and hitchdetection system 22 of the trailer assist system 12 uses inputs receivedfrom a rear-facing camera 18 to determine a relative vehicle-trailerangle in degrees (φ) 30 a and a relative vehicle-trailer angularvelocity (φ) 30 b at a trailer angle detector 22 a. The system 22 alsodetermines a distance from the vehicle rear axle to the hitch point(L_(hitch)) a hitch detector 22 b. The system 12 includes a number ofinput vehicle sensors 19. For example, a steering wheel angle sensor 19a determines an angle of the steering wheel (SWA) and a wheelrevolutions per minute sensor 19 b determines the revolutions per minuteof a vehicle wheel (RPM) respectively.

In some examples, a gyroscope 19 c determines the vehicle yaw rate 34({dot over (θ)}_(G,raw)) and an accelerometer 19 d determines anacceleration rate 36 (a_(lat,raw)) to calculate a vehicle yaw rate 40 ata vehicle yaw rate calculator 38. The vehicle yaw rate 40 may becalculated a number of different ways. For example, the using thesteering wheel angle sensor 19 a and a bicycle kinematic model ofEquation (1) may calculate the vehicle yaw rate 40 (θ_(B)):

$\begin{matrix}{{\overset{.}{\theta}}_{B} = {\frac{V}{L_{wheelbase}}{\tan (\delta)}}} & (1)\end{matrix}$

In Equation (1), V represents the vehicle speed, L_(wheelbase)represents the vehicle's wheelbase, and δ represents the vehicle frontwheel angle (e.g., from a look up table mapping δ to steering wheelangle (SWA)). The vehicle yaw rate 40 (θ_(G)) may also be calculatedusing the gyroscope 19 c with Equation (2):

{dot over (θ)}_(G)={dot over (θ)}_(G,raw){dot over (θ)}_(G,bias)  (2)

In Equation (2), {dot over (θ)}_(G,raw) represents the raw gyroscopemeasurement, while {dot over (θ)}_(G,bias) represents the gyroscope zerobias. The vehicle yaw rate 40 ({dot over (θ)}_(ws)) may also becalculated using differential wheel speeds from the wheel RPM sensors 19b using Equation (3):

$\begin{matrix}{{\overset{.}{\theta}}_{ws} = {\frac{V_{RR} - V_{RL}}{L_{tw}} - {\overset{.}{\theta}}_{{ws},{bias}}}} & (3)\end{matrix}$

In Equation (3), V_(RL) and V_(RR) represent the rear right and the rearleft wheel speeds respectively. The track width is represented by L_(tw)and {dot over (θ)}_(ws, bias) represents zero bias in the yaw ratecalculated from wheel speeds. The vehicle yaw rate 40 ({dot over(θ)}_(a)) may also be calculated using the accelerometer 19 d usingEquation (4):

$\begin{matrix}{{\overset{.}{\theta}}_{a} = \frac{\left( {a_{{lat},{raw}} - a_{{lat},{bias}}} \right)}{V}} & (4)\end{matrix}$

In Equation (4), V represents the vehicle speed, a_(lat,raw) representsthe raw lateral acceleration measurement, and a_(lat, bias) representsthe lateral acceleration zero bias. In some implementations, the vehicleyaw rate 40 may be estimated from any subset of these sensors usingEquation (5):

{dot over (θ)}=w _(B){dot over (θ)}_(B) w _(G){dot over (θ)}_(G) +w_(ws){dot over (θ)}_(ws) +w _(a) {dot over (θ)} _(a)  (5)

In Equation (5), w_(B),w_(G),w_(ws),w_(a) (i.e., each w variable) is anindividual weight for each respective sensor 19 a-d based on, forexample, sensor noise characteristics, resolution, and accuracy ofestimation. That is, each sensor 19 may be individually weighted and thevehicle yaw rate calculation may be estimated based on any subset of thesensors (with the weights shifting accordingly). For example, a moreaccurate and/or reliable sensor 19 may be weighted more than a lessaccurate and/or less reliable sensor 19. A sensor 19 that fails orotherwise fails to meet a threshold of quality and/or reliability may beremoved from the calculation entirely (i.e., a weight of zero).

Responsive to calibration driving maneuvers conducted by a driver of thevehicle (and possibly prompted by the system) and the calculated vehicleyaw rate 40, the trailer angle and hitch detection system 20 outputs 30a, 30 b, 32 (i.e., φ, {dot over (φ)}, and L_(hitch)) and the vehicle yawrate 40 may be used to determine when the relative vehicle-trailerangular velocity reaches an approximate steady-state at steady statedeterminer 44. That is, these outputs are used to determine when therelative trailer angular velocity is below a threshold amount (e.g., ator near zero). In some examples, a front wheel angle 46 (δ) derived atleast in part from a steering wheel angle (SWA) output 42 from thesteering wheel angle sensor 19 a may be determined a wheel angleconverter 48, which in turn may be used to assist in the steady statedetermination at the determiner 44.

The wheel RPM sensor 19 b output, in some implementations, determines aspeed calculation (V) of the vehicle at a speed calculator 50. Forexample, speed may be calculated using the following Equation (6):

V=½(RPM_(rl)+RPM_(rr))·L _(whlcirc)  (6)

In Equation (6), V is vehicle speed (e.g., in meters per second),RPM_(rl) and RPM_(rr) are rear left and rear right wheel revolutions perminute, respectively, and L_(whlcirc) is the effective wheelcircumference (e.g., in meters). In some examples, the driver may berequired to drive the vehicle during calibration maneuvers at a speedthat exceeds a minimum measurement threshold for the wheel RPM sensorsfor the particular vehicle (i.e., the wheel revolves at a rate greaterthan a threshold).

Using the velocity of the vehicle V, the system determines, at thresholddeterminer 52, if the vehicle is moving (i.e., if V is not equal to zeroor is near zero), if the absolute value of the SWA 42 is greater than aminimum threshold steering angle and less than a maximum thresholdsteering angle, and if the absolute value of the change in SWA 42 isless than a threshold steer rate. If all three conditions are true, thesystem enables the steady state determiner 44. That is, the steady statedeterminer 44 always outputs false when not enabled by the thresholddeterminer 52. Otherwise, the steady state determiner 44 outputs true orfalse based on the inputs 30 a, 30 b, 32, 40 as described above.

Referring now to FIG. 3B, if the steady state determiner 44 is enabledand outputs true, the system 12 may determine a steady state trailerbeam length. If the steady state determiner 44 is not enabled and/oroutputs false, the system 12 may determine an unsteady state trailerbeam length calculation. Using vehicle-trailer kinematics, the relativevehicle-trailer angle velocity ({dot over (φ)}) may be calculated using:

$\begin{matrix}{\overset{.}{\phi} = {{\frac{V}{L_{beam}} \cdot {\sin (\phi)}} - {\overset{.}{\theta}\left( {1 + {\frac{L_{hitch}}{L_{beam}}{\cos (\phi)}}} \right)}}} & (7)\end{matrix}$

In Equation (7), φ is the relative vehicle-trailer angle, L_(beam) isthe trailer beam length, and L_(hitch) is the distance from the vehiclerear axle to the hitch point. The vehicle yaw rate is represented by{dot over (θ)} and V still represents the vehicle speed. Based onEquation (7), the unsteady state trailer beam length (i.e., when {dotover (φ)} is not equal to zero or near zero) may be estimated using:

$\begin{matrix}{L_{beam} = {- \left( \frac{{V\sin \; (\phi)} + {L_{hitch}{\cos (\phi)}\overset{.}{\theta}}}{\overset{.}{\phi} + \overset{.}{\theta}} \right)}} & (8)\end{matrix}$

The steady state trailer beam length (i.e., when {dot over (φ)} is equalto zero or near zero) may be estimated using:

$\begin{matrix}{L_{beam} = {- \left( {\frac{V\sin \; (\phi)}{\overset{.}{\theta}} + {L_{hitch}\cos \; (\phi)}} \right)}} & (9)\end{matrix}$

The vehicle-trailer kinematics of Equations (7)-(9) may be dependentupon the assumption that the vehicle and trailer are moving in the samedirection as their wheel direction with proper wheel/ground contact(i.e., neither the vehicle nor the trailer are sliding or slipping).

In some implementations, the calibration driving maneuvers may includesufficient curved paths. For example, the user may not receive the“Calibration Complete” message until sufficient curve to the vehicle'spath is detected. The vehicle may instruct the driver to turn the wheela threshold amount while driving forward to achieve sufficient curve.Still referring to FIG. 3B, the system may ensure a valid trailer beamlength determination (L_(beam,calc)) by determining if L_(beam,calc) isgreater than zero, greater than a lower threshold, lower than an upperthreshold, and not indefinite. If L_(beam,calc) is valid, (i.e., allcriteria are true), then a moving average filter 60 may be applied,which generates L_(beam,avg). The moving average filter, in someexamples, has an infinite sliding window. For example, the movingaverage may be calculated using:

w _(N) =w _(N−1)+1  (10)

and

$\begin{matrix}{{\overset{\_}{x}}_{N} = {\frac{1}{w_{N}}\left( {{w_{N - 1} \cdot {\overset{\_}{x}}_{N - 1}} + x_{N}} \right)}} & (11)\end{matrix}$

The average at the current sample (N) and the previous sample (N−1) isrepresented by x _(N) and x _(N−1) respectively. The number of datapoints at the current sample and previous sample is represented by w_(N)and w_(N−1) respectively and x_(N) represents the current data input.

The determined L_(beam,avg) may then be passed through one or moreconvergence checks 62, and if passed, L_(beam,avg) is stored innon-volatile memory of the vehicle where it may be recalled whenever thesystem detects the respective trailer is hitched.

In some examples, after a minimum number of samples (N), convergencechecks are performed over a subset of subsequent beam lengthcalculations. For example, Equation (12) may determine convergence inprobability:

Pr(| L _(beam,n) − L _(beam,est) |<ε)≥Threshold_(confidence) forn>N  (12)

In Equation (12), L_(beam,est) represents the estimated “true” trailerbeam length from the moving average filter at sample n=n_(o). Thevariable L_(beam,n) represents the sample mean of the trailer beamlength from subsequent calculations (i.e., n>n_(o)). The radius ofconvergence is represented by E.

In some examples, additional criteria to increase accuracy of theestimate includes a monotonicity check:

Threshold_(low) ≤Pr(L _(beam,n)> L _(beam,est) )≤Threshold_(high)  (13)

In Equation (13), L_(beam,n) is the calculated trailer beam length forsample n. If the convergence checks pass, the system may prompt the userwith a message. For example, the system may indicate that calibration iscomplete (e.g., via a display screen in the vehicle). The system maystore L_(beam,est) for use in automated trailering features (e.g.,trailer assist systems). If the convergence checks fail, the estimated“true” trailer beam length may be set to equal the latest sample mean ofthe trailer beam length from the subset L_(beam,est) =L_(beam,n) andthen the convergence checks may be repeated. The system thus includesconvergence criteria in the calculation methodology to provide enhanceddetermination or estimation of the beam length of the trailer beingtowed by the vehicle.

The thresholds described herein (e.g., rate of change thresholds,steering wheel angle thresholds, etc.) may be empirically chosen fornumerical stability of the solution (i.e., the estimation of the trailerbeam length), empirically chosen for measurement and timing errorsinherent in incoming CAN data, and/or derived from first principles toensure operation within the valid regions of the kinematic equations.

Optionally, the trailer assist system bounds the estimated trailer beamlength between a minimum beam length value and a maximum beam lengthvalue to provide a failsafe against aberrant behavior. The drivingmaneuver may be agnostic (e.g., free form driving with now prescribedcalibration maneuvers the driver has to follow) as long as the maneuverhas sufficient curves, while the maneuver may be rejected when themaneuver does not have sufficient curves (e.g., is straight or nearlystraight) in order to be more robust with regards to errant estimatedtrailer beam length due to random variables and disturbances. Forexample, sensor noise, error in state estimation, asynchronous CAN data,environmental factors such as variability in ground conditions, and usercalibration drive maneuver variability may all contribute to an errantestimated trailer beam length.

To derive the maximum steering wheel angle (i.e., Threshold_(steermax)),the vehicle yaw rate {dot over (θ)} may be determined using bicyclekinematics of Equation (14):

$\begin{matrix}{\overset{.}{\theta} = {\frac{V}{L_{wheelbase}}{\tan (\delta)}}} & (14)\end{matrix}$

Combining Equation (9) with Equation (14) yields Equation (15)-(17):

$\begin{matrix}{L_{beam} = {- \left( {{\frac{L_{wheelbase}}{\tan (\delta)}{\sin (\varphi)}} + {L_{hitch}{\cos (\varphi)}}} \right)}} & (15) \\{\frac{dL_{beam}}{d\; \varphi} = {{{- \frac{L_{wheelbase}}{\tan (\delta)}}{\cos (\varphi)}} + {L_{hitch}{\sin (\varphi)}}}} & (16) \\{{{{When}\mspace{14mu} \frac{dL_{beam}}{d\; \varphi}} = 0},{{\tan (\varphi)} = \frac{L_{wheelbase}}{L_{hitch}{\tan (\delta)}}}} & (17)\end{matrix}$

With a constant front wheel angle (δ), the trailer beam length will haveextrema when the relative vehicle-trailer angle (ϕ_(ext)) is equal toEquation (18):

$\begin{matrix}{\varphi_{ext} = {\pm {\tan^{- 1}\left( \frac{L_{wheelbase}}{L_{hitch}{\tan (\delta)}} \right)}}} & (18)\end{matrix}$

For a particular vehicle (i.e., a fixed L_(wheelbase)) and given amaximum hitch length (L_(hitch,max)), the sign of ϕ_(ext) is chosen togive a positive maximum trailer beam length (L_(Beam) _(max) ). Backwardsubstitution derives Equation (19):

$\begin{matrix}{L_{Beam_{\max}} = {- \left( {{\frac{L_{wheelbase}}{\tan (\delta)}{\sin \left( \varphi_{ext} \right)}} + {L_{{hi{tch}},\max}{\cos \left( \varphi_{ext} \right)}}} \right)}} & (19)\end{matrix}$

With a given L_(Beam) _(max) , δ_(max) may be calculated based onNewton's Method using Equation (19). FIG. 4 provides a table for samplecalculations relating maximum front wheel angle (δ_(max)) to the maximumtrailer beam length (L_(Beam) _(max) ). That is, the maximum trailerbeam length is correlated with the maximum front wheel angle.Threshold_(steermax) may be back calculated from δ_(max) using, forexample, the look up table mapping δ to steering wheel angle (SWA).

The trailer beam length may be correlated or associated with thespecific trailer hitched to the vehicle and recalled whenever the systemdetects the same trailer is hitched to the vehicle. The correlation(e.g., a trailer identification) may be stored in non-volatile memorywith the estimated trailer beam length. The system may prompt or accepta variety of calibration driving maneuvers to accurately estimate thetrailer beam length. For example, the vehicle may be driven in a circlewith a fixed or variable steering angle. The vehicle may also be drivenin arcs with various radii, slaloms, or with multiple right and leftturns.

Thus, the system of the present invention determines or estimates orcalculates the trailer beam length with high accuracy to enable betterperformance of other automated trailer features (e.g., backing up,parking, etc.). The driver may switch between trailers and make use ofsuch automated trailer features with minimal setup requirements afterinitially calibrating each trailer. Furthermore, the accuracy of thetrailer beam length estimation is independent from the user skill andmeasurement tool quality which reduced feature performance variabilitybetween users and trailers. The system also eliminates the difficulty ofmeasuring trailer beam length for long and/or multi-axle trailers. Thecalculation methodology includes convergence criteria and is maneuveragnostic. That is, the driver is not required to perform a prescribedcalibration maneuver and instead the system may calibrate from free-formdriving.

The system may utilize aspects of the trailering or trailer angledetection systems or trailer hitch assist systems described in U.S. Pat.Nos. 9,085,261 and/or 6,690,268, and/or U.S. Publication Nos.US-2019-0297233; US-2019-0064831; US-2019-0016264; US-2018-0276839;US-2018-0276838; US-2018-0253608; US-2018-0215382; US-2018-0211528;US-2017-0254873; US-2017-0217372; US-2017-0050672; US-2015-0217693;US-2014-0160276; US-2014-0085472 and/or US-2015-0002670, and/or U.S.patent application Ser. No. 15/929,535, filed May 8, 2020 (AttorneyDocket MAG04 P3842), which are hereby incorporated herein by referencein their entireties.

The system includes an image processor operable to process image datacaptured by the camera or cameras, such as for detecting objects orother vehicles or pedestrians or the like in the field of view of one ormore of the cameras. For example, the image processor may comprise animage processing chip selected from the EYEQ family of image processingchips available from Mobileye Vision Technologies Ltd. of Jerusalem,Israel, and may include object detection software (such as the typesdescribed in U.S. Pat. Nos. 7,855,755; 7,720,580 and/or 7,038,577, whichare hereby incorporated herein by reference in their entireties), andmay analyze image data to detect vehicles and/or other objects.Responsive to such image processing, and when an object or other vehicleis detected, the system may generate an alert to the driver of thevehicle and/or may generate an overlay at the displayed image tohighlight or enhance display of the detected object or vehicle, in orderto enhance the driver's awareness of the detected object or vehicle orhazardous condition during a driving maneuver of the equipped vehicle.

The vehicle may include any type of sensor or sensors, such as imagingsensors or radar sensors or lidar sensors or ultrasonic sensors or thelike. The imaging sensor or camera may capture image data for imageprocessing and may comprise any suitable camera or sensing device, suchas, for example, a two dimensional array of a plurality of photosensorelements arranged in at least 640 columns and 480 rows (at least a640×480 imaging array, such as a megapixel imaging array or the like),with a respective lens focusing images onto respective portions of thearray. The photosensor array may comprise a plurality of photosensorelements arranged in a photosensor array having rows and columns.Preferably, the imaging array has at least 300,000 photosensor elementsor pixels, more preferably at least 500,000 photosensor elements orpixels and more preferably at least 1 million photosensor elements orpixels. The imaging array may capture color image data, such as viaspectral filtering at the array, such as via an RGB (red, green andblue) filter or via a red/red complement filter or such as via an RCC(red, clear, clear) filter or the like. The logic and control circuit ofthe imaging sensor may function in any known manner, and the imageprocessing and algorithmic processing may comprise any suitable meansfor processing the images and/or image data.

For example, the vision system and/or processing and/or camera and/orcircuitry may utilize aspects described in U.S. Pat. Nos. 9,233,641;9,146,898; 9,174,574; 9,090,234; 9,077,098; 8,818,042; 8,886,401;9,077,962; 9,068,390; 9,140,789; 9,092,986; 9,205,776; 8,917,169;8,694,224; 7,005,974; 5,760,962; 5,877,897; 5,796,094; 5,949,331;6,222,447; 6,302,545; 6,396,397; 6,498,620; 6,523,964; 6,611,202;6,201,642; 6,690,268; 6,717,610; 6,757,109; 6,802,617; 6,806,452;6,822,563; 6,891,563; 6,946,978; 7,859,565; 5,550,677; 5,670,935;6,636,258; 7,145,519; 7,161,616; 7,230,640; 7,248,283; 7,295,229;7,301,466; 7,592,928; 7,881,496; 7,720,580; 7,038,577; 6,882,287;5,929,786 and/or 5,786,772, and/or U.S. Publication Nos.US-2014-0340510; US-2014-0313339; US-2014-0347486; US-2014-0320658;US-2014-0336876; US-2014-0307095; US-2014-0327774; US-2014-0327772;US-2014-0320636; US-2014-0293057; US-2014-0309884; US-2014-0226012;US-2014-0293042; US-2014-0218535; US-2014-0218535; US-2014-0247354;US-2014-0247355; US-2014-0247352; US-2014-0232869; US-2014-0211009;US-2014-0160276; US-2014-0168437; US-2014-0168415; US-2014-0160291;US-2014-0152825; US-2014-0139676; US-2014-0138140; US-2014-0104426;US-2014-0098229; US-2014-0085472; US-2014-0067206; US-2014-0049646;US-2014-0052340; US-2014-0025240; US-2014-0028852; US-2014-005907;US-2013-0314503; US-2013-0298866; US-2013-0222593; US-2013-0300869;US-2013-0278769; US-2013-0258077; US-2013-0258077; US-2013-0242099;US-2013-0215271; US-2013-0141578 and/or US-2013-0002873, which are allhereby incorporated herein by reference in their entireties. The systemmay communicate with other communication systems via any suitable means,such as by utilizing aspects of the systems described in InternationalPublication Nos. WO 2010/144900; WO 2013/043661 and/or WO 2013/081985,and/or U.S. Pat. No. 9,126,525, which are hereby incorporated herein byreference in their entireties.

Optionally, the vision system may include a display for displayingimages captured by one or more of the imaging sensors for viewing by thedriver of the vehicle while the driver is normally operating thevehicle. Optionally, for example, the vision system may include a videodisplay device, such as by utilizing aspects of the video displaysystems described in U.S. Pat. Nos. 5,530,240; 6,329,925; 7,855,755;7,626,749; 7,581,859; 7,446,650; 7,338,177; 7,274,501; 7,255,451;7,195,381; 7,184,190; 5,668,663; 5,724,187; 6,690,268; 7,370,983;7,329,013; 7,308,341; 7,289,037; 7,249,860; 7,004,593; 4,546,551;5,699,044; 4,953,305; 5,576,687; 5,632,092; 5,708,410; 5,737,226;5,802,727; 5,878,370; 6,087,953; 6,173,501; 6,222,460; 6,513,252 and/or6,642,851, and/or U.S. Publication Nos. US-2014-0022390;US-2012-0162427; US-2006-0050018 and/or US-2006-0061008, which are allhereby incorporated herein by reference in their entireties.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

1. A vehicular trailering assist system, the vehicular trailering assistsystem comprising: a camera disposed at a rear portion of a vehicle andhaving a field of view exterior and at least rearward of the vehicle,the vehicle having a hitch configured for hitching a trailer at thevehicle, the hitch being at a location spaced from a rear axle of thevehicle, the field of view of the camera including at least a portion ofa trailer hitched to the vehicle at the hitch of the vehicle; a steeringwheel angle sensor operable to determine a steering wheel angle of thevehicle; a wheel revolutions per minute (RPM) sensor operable todetermine an RPM of a wheel of the vehicle; a control comprisingelectronic circuitry and associated software; wherein said electroniccircuitry of said control comprises at least one data processor forprocessing image data captured by the camera and sensor data captured by(i) the steering wheel angle sensor and (ii) the wheel RPM sensor;wherein the control, responsive to processing at the control of imagedata captured by the camera, determines a trailer angle of the trailerrelative to the vehicle; wherein the control determines the steeringwheel angle of the vehicle via sensor data provided to the control fromthe steering wheel angle sensor; wherein the control determines thewheel RPM of the wheel of the vehicle via sensor data provided to thecontrol from the RPM sensor; and wherein the control estimates a trailerbeam length of the trailer based on at least (i) the determined trailerangle relative to the vehicle, (ii) the determined steering wheel angleof the vehicle and (iii) the determined wheel RPM of the wheel of thevehicle.
 2. The vehicular trailering assist system of claim 1, whereinthe control estimates the trailer beam length of the trailer based inpart on a hitch location of the hitch relative to the rear axle of thevehicle.
 3. The vehicular trailering assist system of claim 1, whereinthe control, based on the steering wheel angle, determines a wheel angleof a front wheel of the vehicle.
 4. The vehicular trailering assistsystem of claim 1, wherein the control, based on the RPM of the wheel ofthe vehicle, determines a speed of the vehicle.
 5. The vehiculartrailering assist system of claim 1, wherein the control determines arate of change of the trailer angle.
 6. The vehicular trailering assistsystem of claim 5, wherein the control, responsive to the rate of changeof the trailer angle being non-zero, estimates an unsteady state trailerbeam length of the trailer.
 7. The vehicular trailering assist system ofclaim 5, wherein the control, responsive to the rate of change of thetrailer angle being zero, estimates a steady state trailer beam lengthof the trailer.
 8. The vehicular trailering assist system of claim 1,wherein the control, responsive to estimating the trailer beam length ofthe trailer, verifies the trailer beam length passes at least oneconvergence check.
 9. The vehicular trailering assist system of claim 1,wherein the control, responsive to estimating the trailer beam length ofthe trailer, correlates the trailer beam length to the specific trailerhitched to the vehicle and stores the trailer beam length andcorrelation in non-volatile memory.
 10. The vehicular trailering assistsystem of claim 1, wherein the control, responsive to estimating thetrailer beam length of the trailer, determines an average trailer beamlength using a moving average filter.
 11. The vehicular traileringassist system of claim 10, wherein the moving average filter has aninfinite sliding window.
 12. The vehicular trailering assist system ofclaim 1, comprising a gyroscope and an accelerometer, wherein thecontrol, responsive to processing sensor data captured by the gyroscopeand the accelerometer, determines a vehicle yaw rate.
 13. The vehiculartrailering assist system of claim 1, wherein the control determines ayaw rate of the vehicle based at least in part on processing of sensordata captured by the steering wheel angle sensor and the RPM sensor. 14.The vehicular trailering assist system of claim 1, wherein the estimatedtrailer beam length of the trailer is bounded between a minimumestimated trailer beam length and a maximum estimated trailer beamlength.
 15. A vehicular trailering assist system, the vehiculartrailering assist system comprising: a camera disposed at a rear portionof a vehicle and having a field of view exterior and at least rearwardof the vehicle, the vehicle having a hitch configured for hitching atrailer at the vehicle, the hitch being at a location spaced from a rearaxle of the vehicle, the field of view of the camera including at leasta portion of a trailer hitched to the vehicle at the hitch of thevehicle; a steering wheel angle sensor operable to determine a steeringwheel angle of the vehicle; a wheel revolutions per minute (RPM) sensoroperable to determine an RPM of a wheel of the vehicle; a controlcomprising electronic circuitry and associated software; wherein saidelectronic circuitry of said control comprises at least one dataprocessor for processing image data captured by the camera and sensordata captured by (i) the steering wheel angle sensor and (ii) the wheelRPM sensor; wherein the control, responsive to processing at the controlof image data captured by the camera, determines a trailer angle of thetrailer relative to the vehicle; wherein the control determines thesteering wheel angle of the vehicle via sensor data provided to thecontrol from the steering wheel angle sensor; wherein the controldetermines the wheel RPM of the wheel of the vehicle via sensor dataprovided to the control from the RPM sensor; wherein the control, basedon the determined steering wheel angle, determines a wheel angle of afront wheel of the vehicle; and wherein the control estimates a trailerbeam length of the trailer based on at least (i) the determined trailerangle relative to the vehicle, (ii) the determined wheel angle of thefront wheel of the vehicle, (iii) the determined wheel RPM of the wheelof the vehicle and (iv) a hitch location of the hitch relative to therear axle of the vehicle.
 16. The vehicular trailering assist system ofclaim 15, wherein the control, responsive to estimating the trailer beamlength of the trailer, verifies the trailer beam length passes at leastone convergence check.
 17. The vehicular trailering assist system ofclaim 15, wherein the control, responsive to estimating the trailer beamlength of the trailer, correlates the trailer beam length to thespecific trailer hitched to the vehicle and stores the trailer beamlength and correlation in non-volatile memory.
 18. The vehiculartrailering assist system of claim 15, wherein the control, responsive toestimating the trailer beam length of the trailer, determines an averagetrailer beam length using a moving average filter.
 19. The vehiculartrailering assist system of claim 18, wherein the moving average filterhas an infinite sliding window.
 20. A vehicular trailering assistsystem, the vehicular trailering assist system comprising: a cameradisposed at a rear portion of a vehicle and having a field of viewexterior and at least rearward of the vehicle, the vehicle having ahitch configured for hitching a trailer at the vehicle, the hitch beingat a location spaced from a rear axle of the vehicle, the field of viewof the camera including at least a portion of a trailer hitched to thevehicle at the hitch of the vehicle; a steering wheel angle sensoroperable to determine a steering wheel angle of the vehicle; a wheelrevolutions per minute (RPM) sensor operable to determine an RPM of awheel of the vehicle; a control comprising electronic circuitry andassociated software; wherein said electronic circuitry of said controlcomprises at least one data processor for processing image data capturedby the camera and sensor data captured by (i) the steering wheel anglesensor and (ii) the wheel RPM sensor; wherein the control, responsive toprocessing at the control of image data captured by the camera,determines a trailer angle of the trailer relative to the vehicle;wherein the control determines the steering wheel angle of the vehiclevia sensor data provided to the control from the steering wheel anglesensor; wherein the control determines the wheel RPM of the wheel of thevehicle via sensor data provided to the control from the RPM sensor;wherein the control determines a rate of change of the trailer angle;wherein the control, responsive to the rate of change of the trailerangle being non-zero, estimates an unsteady state trailer beam length ofthe trailer based on at least (i) the determined trailer angle relativeto the vehicle, (ii) the determined steering wheel angle of the vehicleand (iii) the determined wheel RPM of the wheel of the vehicle; andwherein the control, responsive to the rate of change of the trailerangle being zero, estimates a steady state trailer beam length of thetrailer based on at least (i) the determined trailer angle relative tothe vehicle, (ii) the determined steering wheel angle of the vehicle and(iii) the determined wheel RPM of the wheel of the vehicle.
 21. Thevehicular trailering assist system of claim 20, comprising a gyroscopeand an accelerometer, wherein the control, responsive to processingsensor data captured by the gyroscope and the accelerometer, determinesa vehicle yaw rate.
 22. The vehicular trailering assist system of claim20, wherein the control determines a yaw rate of the vehicle based atleast in part on processing of sensor data captured by the steeringwheel angle sensor and the RPM sensor.